An image sensor is a kind of semiconductor device that transforms optical images into electrical signals. Image sensors can be generally classified into charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) image sensors. Among these image sensors, a CMOS image sensor comprises a photodiode for detecting incident light and transforming it into electrical signals, and logic circuits for transmitting and processing the electrical signals. A CMOS image sensor includes a light sensing part having a plurality of photodiodes for accepting incident light, and for generating and accumulating electric charges, a protecting layer formed on a structure of the light sensing part, a color filter array, and a plurality of micro-lenses. The color filter array can be formed in a primary color system, i.e., comprising red filters (R), green filters (G), and blue filters (B), using photoresist materials containing a red, green, or blue pigment, respectively. Formation of each color filter involves a series of coating, exposure and development processes according to photolithography techniques. Alternatively, the color filter array can be formed in a complementary color system comprising cyan, yellow, and magenta filters.